Packaging box assembly with a changeable size

ABSTRACT

A packaging box assembly includes a base plate, a middle plate set and a cover plate. The base plate has a central wall, and a plurality of lateral walls extending from the central wall. The lateral walls are foldable along fold lines to define a receiving space with the central wall. The middle plate set is placed within the receiving space and is changeable between a cushioning position in which the middle plate set is parallel to the central wall, and an assembled position in which the middle plate set is perpendicular to the central wall. When the middle plate set is in the cushioning position, the cover plate is placed on top of the base plate. When the middle plate set is in the assembled position, the cover plate is placed on the middle plate set. Thus, various modular configurations are formed to change the size of the box assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Application No. 095132166, filed on Aug. 31, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a packaging box assembly, more particularly to a packaging box assembly formable into interchangeable modular configurations so that the size thereof can be varied.

2. Description of the Related Art

Currently available packaging boxes are generally designed for particular sizes of products so that they cannot be used widely.

Take a computer housing as an example. As shown in FIG. 1, an earlier computer housing 11 is bulky and thus requires a big packaging box. During transport, the packaging box not only occupies a considerable space but also is difficult to carry. For that reason, some manufacturers have designed a foldable computer housing, such as that shown at 12 in FIG. 2. The volume of a box for packing the foldable computer housing 12 is small, thereby saving space and facilitating transport.

However, since the currently available computer housings have different configurations which are significantly different in size as shown in FIGS. 1 and 2, an exclusive packing box has to be used for each individual configuration. In other words, a box for packaging the computer housing 11 of FIG. 1 cannot be used for packaging the computer housing 12 shown in FIG. 2. Also, a box for packaging the computer housing 12 shown in FIG. 2 cannot be used for packaging the computer housing 11 of FIG. 1. The exclusive nature of the conventional packing boxes reduces the possibility of reusing the packing boxes. In addition, manufacturers have to provide packing boxes with various sizes in order to satisfy the requirements of packaging differently sized computer housings. As a result, manufacturing costs are increased, and environmental protection requirements cannot be met.

SUMMARY OF THE INVENTION

Therefore, the main object of the present invention is to provide a packaging box assembly with interchangeable modular configurations that have different sizes.

According to one aspect of the present invention, a packaging box assembly comprises a base plate, a middle plate set and a cover plate. The base plate has a central wall, a plurality of lateral walls extending respectively from lateral ends of the central wall, and a plurality of fold lines. The fold lines are formed between the central wall and the lateral walls and in the lateral walls so that the base plate is foldable to form a receiving space defined by the central wall and the lateral walls.

The middle plate set is disposed within the receiving space and is changeable between a cushioning position in which said middle plate set is disposed parallel to the central wall, and an assembled position in which the middle plate set is perpendicular to the central wall. The cover plate closes the receiving space and is positioned on top of the lateral walls of the base plate when the middle plate set is in the cushioning position. The cover plate is positioned on top of the middle plate set when the middle plate set is in the assembled position.

According to another aspect of the present invention, a packaging box assembly comprises a base plate, a cover plate and a middle plate set. The base plate has a central wall, and a plurality of lateral walls extending perpendicularly from the central wall. The central wall and the lateral walls confine a receiving space. A cover plate closes the receiving space. The cover plate has a central wall, and a plurality of lateral walls extending perpendicularly from the central wall of the cover plate. The central wall and the lateral walls of the cover plate confine another receiving space.

The middle plate set includes inner middle plates interlockable with the base plate to extend perpendicularly relative to the central wall of the base plate and to abut against inner surfaces of the lateral walls of the base plate, and outer middle plates interlockable with the cover plate to extend perpendicularly relative to the central wall of the cover plate and to abut against inner surfaces of the lateral walls of the cover plate. The inner and outer middle plates are higher than the lateral walls of the base plate and the cover plate, respectively.

When the inner and outer middle plates interlock with the base plate and the cover plate, the outer middle plates can be sleeved around the inner middle plates to form a first box configuration. When the inner and outer middle plates are separated from the lateral walls of the base plate and the cover plate, the lateral walls of the cover plate can rest on top ends of the lateral walls of the base plate, respectively, to form a second box configuration.

According to further aspect of the present invention, a packaging box assembly comprises a base plate and a plurality of inner middle plates. The base plate has a central wall, and a plurality of lateral walls extending substantially perpendicularly from the central wall. The central wall and the lateral walls confine a receiving space.

The inner middle plates are disposed perpendicularly on the central wall and abut against inner surfaces of the lateral walls. The inner middle plates are higher than the lateral walls. At least one of the inner middle plates interlocks releasably with the base plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:

FIG. 1 is a schematic view of a conventional computer housing;

FIG. 2 is a schematic view of an existing collapsible and foldable computer housing;

FIG. 3 is a plan view of a base plate of a packaging box assembly according to the preferred embodiment of the present invention, wherein the base plate is unfolded;

FIG. 4 is a perspective view of two inner middle plates of the preferred embodiment in an unfolded state;

FIG. 5 is a plan view of an outer middle plate of the preferred embodiment in an unfolded state;

FIG. 6 is a plan view of a cover plate of the preferred embodiment in an unfolded state;

FIG. 7 is a plan view of an auxiliary cover plate of the preferred embodiment in an unfolded state;

FIG. 8 is a perspective view of the two inner middle plates and the base plate, the two inner middle plates being folded in half;

FIG. 9 is a perspective view of the partially assembled box assembly of the preferred embodiment, wherein the two inner middle plates are superimposed upon the base plate, and the first and second lateral walls of the base plate are folded;

FIG. 10 is a schematic view of the preferred embodiment, showing the structural relationship, before assembly, among the cover plate, the foldable computer housing, and the base plate receiving the inner middle plates;

FIG. 11 is another schematic view of the preferred embodiment, showing that the auxiliary cover plate is in an unfolded state;

FIG. 12 is a schematic view of the preferred embodiment in an assembled state, showing that the foldable computer housing and its related accessory are assembled in the packaging box assembly;

FIG. 13 is a fragmentary view of the preferred embodiment, showing that a second limit plate of one of the inner middle plates extends outward through a second engaging hole of the base plate and is bent and inserted into another second engaging hole;

FIG. 14 is still another schematic view of the preferred embodiment, showing the relationship, before assembly, among the cover plate receiving the outer middle plates, a non-foldable computer housing, and the base plate receiving the inner middle plate;

FIG. 15 is yet another schematic view of the preferred embodiment, showing the non-foldable computer housing and its related accessory, which are assembled in the packaging box assembly; and

FIG. 16 is a fragmentary sectional view of a portion (A) in FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 3-7, a preferred embodiment of a packaging box assembly according to the present invention includes a base plate 3 (see FIG. 3), a middle plate set 4 (see FIGS. 4, 5), a cover plate 5 (see FIG. 6), and an auxiliary cover plate 6 (FIG. 7).

As shown in FIG. 3, the base plate 3 has a substantially rectangular central wall 31, a plurality of lateral walls extending laterally from lateral ends of the central wall 31 and having a generally rectangular shape (i.e., two opposite first and second lateral walls 32, 33, and two opposite third and fourth lateral walls 34, 35), and a plurality of fold lines 36 (shown in dotted lines). In the central wall 31, there are provided a plurality of first engaging holes 311 proximate to the first to fourth lateral walls 32˜35. Besides, each of the first to fourth lateral walls 32˜35 is divided by two fold lines 36 to form first regions 321, 331, 341, 351 proximate to the central wall 31, second regions 322, 332, 342, 352 distal from the central wall 31, and connection regions 323, 333, 343, 353 extending between the first regions 321, 331, 341, 351 and the second regions. Each of the second regions 322, 332, 342, 352 of the first to fourth lateral walls 32, 33, 34, 35 has an outer longitudinal lateral end provided with connecting tabs 324, 334, 344, 354 opposite to the respective first engaging holes 311. Each of the first and second regions 321, 331, 322, 332 of the first and second lateral walls 32, 33 has two opposite ends respectively provided with two wing plates 325 or 335 projecting therefrom. The wing plates 325, 335 are provided respectively with third engaging holes 326, 336 proximate to the respective first and second regions 321, 331, 322, 332.

Furthermore, an ear part 327 projects from the second region 322 of the first lateral wall 32, and has an opening 328. The connection region 323 of the first lateral wall 32 has two spaced apart fastening holes 329. Each of the third and fourth lateral walls 34, 35 is provided with second engaging holes 345, 355 proximate to the central wall 31 and in the connection regions 343, 353. Every two of the second engaging holes 345, 355 in each of the third and fourth lateral walls 34, 35 are aligned with each other in a direction substantially perpendicular to the fold lines 36 formed in the third and fourth lateral walls 34, 35. After each lateral wall 32, 33, 34, 35 is folded in half, the connecting tabs 324, 334, 344, 354 in each lateral wall 32, 33, 34 or 35 can be inserted into the respective first engaging holes 321, 331, 341, 351, and every two aligned second engaging holes 345, 355 can be placed one above the other. Further, the second regions 342, 352 of the third and fourth lateral walls 34, 35 are provided with lateral connecting plates 346, 356 proximate to the respective wing plates 325, 335.

The middle plate set 4 includes two rectangular inner middle plates 41 which are mirror images of each other (as shown in FIG. 4), and two rectangular outer middle plates 42 (only one is shown in FIG. 5) which are mirror images of each other. As shown in FIG. 4, each inner middle plate 41 has two spaced-apart first limit plates 411 projecting from a longitudinal edge of the inner middle plate 41 proximate to one end thereof, and two spaced-apart second limit plates 412 projecting from the same longitudinal edge proximate to the other end thereof. The second limit plates 412 are longer than the first limit plates 411. Each inner middle plate 41 further has a middle part provided with a linking hole 413, a first linking plate 414 which projects from one end of the respective inner middle plate 41 proximate to the first limit plates 411 and which has a first connecting hole 415 formed therein adjacent to the respective first linking plate 414. Besides, as shown in FIG. 5, the outer middle plate 42 is provided with a plurality of fold lines 43 (shown in dotted lines). A second connecting plate 421 projects from one end of the outer middle plate 42 and has a second connecting hole 422. Third and fourth connecting plates 423, 424 are formed respectively at another end and in a middle section of the respective outer middle plate 42 by using split lines 44. Two third limit plates 425 and two fourth limit plates 426 project from a longitudinal edge of the outer middle plate 42 in a spaced apart relationship.

As shown in FIG. 6, the cover plate 5 has a structural design substantially similar to that of the base plate 3, and includes similar component parts, such as a rectangular central wall 51, two opposite first and second lateral walls 52, 53, two opposite third and fourth lateral walls, and a plurality of fold lines 36 (shown in dotted lines). The central wall 51 has a plurality of first engaging holes 511 proximate to the lateral walls 52, 53, 54, 55, respectively. Each of the third and fourth lateral walls 54, 55 has a plurality of spaced apart second engaging holes 545, 555. Every two of the second engaging holes 545, 555 are aligned with each other. Each lateral wall 52, 53, 54, 55 further has connecting tabs 524, 534, 544, 554 projecting from one lateral end thereof, which is distal from the central wall 51. After each lateral wall 52, 53, 54, 55 is folded in half, the connecting tabs 524, 534, 544, 554 thereof can be inserted into the respective first engaging holes 511, and every two engaging holes 545, 555 can be placed one above the other.

Each of the first and second lateral walls 52, 53 has two wing plates 525, 535 respectively provided at two opposite ends of each of first and second regions 521, 531, 522, 532 thereof. The wing plates 525, 535 respectively have third engaging holes 526, 536 proximate to the first and second regions 521, 531, 522, 532. The second regions 542, 552 of the third and fourth lateral walls 54, 55 have lateral connecting plates 546, 556 projecting therefrom proximate to the respective wing plates 525, 535. When the lateral walls 52, 53, 54, 55 of the cover plate 5 are folded in half, the third engaging holes 525, 535 in two adjacent wing plates 525, 535 are communicated with each other to permit insertion of the respective lateral connecting plates 546, 556.

The cover plate 5 differs from the base plate 3 in that the first lateral wall 52 is not provided with any ear part similar to the ear part 327 of the base plate 3. A fifth linking plate 57 is formed adjacent to a juncture between the central wall 51 and the first lateral wall 52 by providing a first split line 56. Moreover, a sixth linking plate 59 is formed in the central wall 51 and away from the fifth linking plate 57 by providing a substantially U-shaped second split line 56 and fold lines 58. An insert hole 521 is formed in the first lateral wall 52 adjacent to the central wall 51 for insertion of the ear part 327 of the base plate 3.

Referring to FIG. 7, the auxiliary cover plate 6 is divided by a plurality of fold lines 61 to form a rectangular middle area 62, and first, second third, fourth lateral areas 63, 64, 65, 66 disposed around the middle area 62. The middle area 62 is provided with a plurality of elongated slots 621 proximate to the first lateral area 63. The second lateral area 64 has a width larger than that of the first lateral area 63 and serves as an attachment area, which may be provided with a layer of adhesive, or a double-sided adhesive tape. The third and fourth lateral areas 65, 66 are opposite to each other and each have an engagement plate 651, 661 projecting therefrom. Besides, the fold lines 61 are provided at the connections of the middle area 62 with the first, second, third and fourth lateral areas 63, 64, 65 and 66.

When the packaging box assembly 2 of the present invention is used for packaging a folded computer housing like the one shown in FIG. 2, the components of the packaging box assembly 2 may be folded and assembled as follows:

Firstly, the two inner middle plates 41 shown in FIG. 4 are folded in half and are placed on the central wall 31 of the base plate 3 in opposite directions, as shown in FIG. 8. Thereafter, the first, second, third, and fourth lateral walls 32, 33, 34, 35 of the base plate 3 are folded along the fold lines 36, and the connecting tabs 324, 334 of the second regions 322, 332 of the first and second lateral walls 32, 33 are inserted into the respective first engaging holes 311. At this state, the second regions 322, 332 of the lateral walls 32, 33 are folded backward over the respective first regions 321, 331 and extend to the central wall 311, and the connection regions 323, 333 extend in a plane parallel to the central wall 311. Further, the wing plates 325, 335 at the two ends of the first and second lateral walls 32, 33 are bent inward by 90 degrees to form a configuration shown in FIG. 9. At this juncture, the cross section of each of the first and second lateral walls 32, 33 has an inverted U-shape, wherein the connection regions 323, 333 of the first and second lateral walls 32, 33 face upward. The wing plates 325 or 335 at the two ends of the first and second lateral walls 32, 33 lie one over the other, and the third engaging holes 326, 336 in the wing plates 325, 335 are aligned with each other. Besides, the first linking plates 414 of each inner middle plate 41 are constrained to bend by 90 degrees.

Referring back to FIGS. 3, 8 and 9, the third and fourth lateral walls 34, 35 are folded similarly along the fold lines 36, and the connecting tabs 344, 354 on the second regions 342, 352 of the third and fourth lateral walls 34, 35 are inserted into the respective first engaging holes 311 adjacent to the central wall 31 (see FIG. 8). At the same time, the lateral connecting plates 346, 356 of the third and fourth lateral walls 34, 35 are respectively inserted into two aligned third engaging holes 326, 336 so that the base plate 3 and the two inner middle plates 41 are assembled together, as shown in FIG. 10. As such, the first, second, third and fourth lateral walls 32˜35 of the base plate 3 cooperatively define a receiving space 37. The inner middle plates 41 are placed in their cushioning position within the receiving space 37, in which the inner middle plates 41 are parallel to the central wall 31.

Because the cover plate 5 is assembled in a manner similar to that of the base plate 3 as shown in FIGS. 6 to 10, assembly of the cover plate 5 is not described herein for the sake of brevity. Referring back to FIG. 10, after the packaging box assembly 2 is folded and assembled in the manner as described above, it may be used to receive a folded computer housing 81. When the computer housing 81 is put into the receiving space 37, the inner middle plates 41 situated within the receiving space 37 will serve as a cushion for the computer housing 81 and protect the same from impacts. Then, the folded cover plate 5 is placed on top of the folded base plate 3, the ear part 327 of the base plate 3 is inserted into the insert hole 521 in the cover plate 5, and the fifth linking plate 57 of the cover plate 5 is inserted into the opening 328 in the ear part 327. As such, the cover plate 5 is assembled on the base plate 3 as shown in FIG. 11.

Afterwards, another computer-related accessory, such as a keyboard 82, may be placed on the cover plate as shown in FIGS. 11 and 12. As described hereinbefore, the second lateral area 64 (the attachment area) of the auxiliary cover plate 6 is provided with the adhesive layer (or the double-sided adhesive tape). Therefore, the second lateral area 64 (the attachment area) can be adhered to the first regions 331, 531 of the second lateral walls 33, 53 of the base plate 3 and the cover plate 5, which are at the same side. Subsequently, the auxiliary cover plate 6 is folded along the fold lines 61 such that the central area 62 is superimposed upon the keyboard 82. Then, the engaging plates 651, 661 of the third and fourth lateral areas 65, 66 are inserted into the respective second engaging holes 545, 555 of the cover plate 5, the first lateral area 63 is folded to extend beneath the keyboard 82, the sixth linking plate 59 on the cover plate 5 is folded and inserted into the respective elongated slot 621 in the auxiliary cover plate 6, and the fifth linking plate 57 is inserted into the opening 328 (see FIG. 10) in the ear part 327 of the base plate 3. FIG. 12 shows that the folded computer housing 81 and the keyboard 82 are packed in the packaging box assembly 2. In order to facilitate carrying of the packaging box assembly 2, a handle 83 may be attached to the base plate 3 in the fastening holes 329.

When the packaging box assembly 2 is to pack an unfoldable computer housing like the one shown in FIG. 1, each of the two inner middle plates 41, which are in an unfolded state as shown in FIG. 4, is folded by 90 degrees, and is placed perpendicularly on the central wall 31 of the base plate 3 (see FIG. 14) so that the inner middle plates 41 are in an upright assembled position. Reference is made to FIGS. 13 and 14 in combination with FIGS. 3 and 4. The base plate 3 is subsequently folded as described hereinbefore. After folding the base plate 3, the first limit plates 411 of each of the inner middle plates 41 are inserted between the respective first region 341, 351 and the respective second region 342, 352 of the third or fourth lateral wall 34, 35 of the base plate 3. As shown in FIG. 13, the second limit plates 412 of each of the two inner middle plates 41 extend outward through the respective second engaging holes 345 (355) in the third lateral wall 34 (fourth lateral wall 35) adjacent to the central wall 31 (FIG. 14) and are subsequently folded and inserted into the respective second engaging holes 345 (355) formed in the connection region 343 (353). Thus, the two inner middle plates 41 are assembled in the receiving space 37 of the base plate 3 in such a manner that the inner middle plates 41 abut against inner surfaces of the first, second, third and fourth lateral walls 32, 33, 34, 35. At this time, a computer housing 84 may be placed within a space defined by the two inner middle plates 41 and the central wall 31 of the base plate 3.

Referring back to FIGS. 5, 6 and 14, after the cover plate 5 is folded and assembled in a fashion as described hereinafter, the two outer middle plates 42 are assembled within the cover plate 5 in a manner similar to that of the two inner middle plates 41 disposed in the base plate 3. In particular, the two third limit plates 425 of each outer middle plate 42 extend between the respective first region 541, 551 and the respective second region 542, 552 of the third or fourth lateral wall 54 or 55. Like the second limit plate 412 of the inner middle plate 41 shown in FIG. 13, the fourth limit plates 426 are also folded and inserted into the respective second engaging holes 545, 555 in the connection regions 543, 553 of the cover plate 5. Further, the two outer middle plates 42 are interconnected as a unitary body by interlocking each second connecting hole 422 with the respective third linking plate 423, as shown in FIG. 14. The outer middle plates 42 and the cover plate 5 cooperatively define a space which is larger than the receiving space defined by the two inner middle plates 41 and the central wall 31 of the base plate 3. Therefore, the outer middle plates 42 can be sleeved onto the inner middle plates 41, as shown in FIGS. 15 and 16. Then, the fourth linking plates 424 (FIG. 5) of the outer middle plates 42 are inserted into the respective linking holes 413 (FIG. 4), and the third linking plates 423 of the outer middle plates 42 are inserted into the respective first connecting holes 415 (FIG. 16), thereby completing the operation of packaging the computer housing 84 with the packaging box assembly 2.

Of course, a computer-related accessory, such as the keyboard 82, may be placed on the cover plate 5 in a manner as illustrated in FIG. 12 and may be fixed on the cover plate 5 using the auxiliary cover plate 6.

As described hereinabove, in the packaging box assembly 2 according to the present invention, by means of the central wall 31 of the base plate 3 and the multiple fold lines 36 provided in the multiple lateral walls 32˜35 extending from the central wall 31, the central wall 31 and the lateral walls 32˜35 cooperatively define the receiving space 37. With the two inner middle plates 41 provided in the receiving space 37 in a cushioning position, the folded computer housing 81 (see FIG. 10) may be placed within the receiving space 37. The inner middle plates 41 serve as a buffering material to protect the computer housing 81 against impact. On the other hand, with the use of the auxiliary cover plate 6, the related accessory 82 may be packed in the packaging box assembly 2. In addition, when the inner middle plates 41 are changed into the upright assembled position and are perpendicular to the central wall 31, and when the two outer middle plates 42 are assembled on the cover plate 5, the volume of the packaging box 2 becomes large and can receive the unfoldable computer housing 84 (see FIG. 14). Therefore, the packaging box assembly 2 has interchangeable modular configurations to permit changes in size of the packaging box assembly 2.

Note that the inner middle plates 41 are higher than the lateral walls 32, 33, 34, 35 of the base plate 3 and interlock releasably with the base plate 3 through the second engaging holes 345, 355 formed in the third and fourth lateral walls 34, 35 (see FIGS. 3, 4, 14, 15 and 16). When the inner and outer middle plates 41, 42 interlock with the base plate 3 and the cover plate 5, the outer middle plates 42 can be sleeved around the inner middle plates 41 to form a first box configuration (see FIGS. 14, 15). When the inner and outer middle plates 41, 42 are separated respectively from the lateral walls 32, 33, 34, 35 of the base plate 3 and the lateral walls 52, 53, 54, 55 of the cover plate 5, the lateral walls 52, 53, 54, 55 of the cover plate 5 can rest on top ends of the lateral walls 32, 33, 34, 35 of the base plate 3, respectively, to form a second box configuration (see FIGS. 9, 10, 11 and 12).

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

1. A packaging box assembly comprising: a base plate having a central wall, a plurality of lateral walls extending respectively from lateral ends of said central wall, and a plurality of fold lines, said fold lines being formed between said central wall and said lateral walls and in said lateral walls so that said base plate is foldable to form a receiving space defined by said central wall and said lateral walls; a middle plate set disposed within said receiving space and changeable between a cushioning position in which said middle plate set is disposed parallel to said central wall, and an assembled position in which said middle plate set is perpendicular to said central wall; and a cover plate to close said receiving space, said cover plate being positioned on top of said lateral walls of said base plate when said middle plate set is in said cushioning position, said cover plate being positioned on top of said middle plate set when said middle plate set is in said assembled position.
 2. The packaging box assembly of claim 1, wherein said central wall of said base plate has a plurality of first engaging holes proximate to said lateral walls, said lateral walls including two opposite first and second lateral walls, and two opposite third and fourth lateral walls, each of said third and fourth lateral walls having a plurality of spaced apart second engaging holes, every two of said second engaging holes in each of said third and fourth lateral walls being aligned with each other, each of said lateral walls further having one lateral end which is distal from said central wall and which has at least one connecting tab projecting therefrom, wherein, after each of said lateral walls is folded, said connecting tab in each of said lateral walls can be inserted into a respective one of said first engaging holes, and said every two of said second engaging holes can be placed one above the other.
 3. The packaging box assembly of claim 2, wherein said first, second, third and fourth lateral walls are each divided by two of said fold lines into a first region proximate to said central wall, a second region distal from said central wall, and a connection region between said first and second regions, said connecting tab being disposed at a longitudinal side of said second region of each of said lateral walls and being aligned with a respective one of said first engaging holes.
 4. The packaging box assembly of claim 3, further comprising a handle, said connection region of said first lateral wall of said base plate having two spaced apart fastening holes, said handle being fixed in said fastening holes.
 5. The packaging box assembly of claim 2, wherein each of said first and second lateral walls of said base plate has two wing plates respectively provided at two opposite ends of each of said first and second regions of said first and second lateral walls, said wing plates respectively having third engaging holes proximate to said first and second regions of said first and second lateral walls, said second regions of said third and fourth lateral walls of said base plate having lateral connecting plates projecting therefrom proximate to the respective ones of said wing plates, whereby, after said lateral walls of said base plate are folded, said third engaging holes in two adjacent ones of said wing plates are communicated with each other to permit insertion of a respective one of said lateral connecting plates therein.
 6. The packaging box assembly of claim 5, wherein said cover plate has a central wall, a plurality of lateral walls extending respectively from lateral ends of said central wall of said cover plate, and a plurality of fold lines, said fold lines of said cover plate extending between said central wall of said cover plate and said lateral walls of said cover plate and in said lateral walls of said cover plate, said central wall and said lateral wall of said cover plate being foldable along said fold lines of said cover plate to define a space.
 7. The packaging box assembly of claim 6, wherein said central wall of said cover plate has a plurality of first engaging holes proximate to said lateral walls of said cover plate, said lateral walls of said cover plate including two opposite first and second lateral walls, and two opposite third and fourth lateral walls, each of said third and fourth lateral walls of said cover plate having a plurality of spaced apart second engaging holes, every two of said second engaging holes in said third and fourth lateral walls of said cover plate being aligned with each other, each of said lateral walls of said cover plate further having one lateral end which is distal from said central wall of said cover plate and which has at least one connecting tab projecting therefrom, wherein, after each of said lateral walls of said cover plate is folded, said connecting tab of said cover plate in each of said lateral walls of said cover plate can be inserted into a respective one of said first engaging holes of said cover plate, and said every two of said second engaging holes of said cover plate can be placed one above the other.
 8. The packaging box assembly of claim 7, wherein said middle plate set includes two inner middle plates of identical shape, each of said inner middle plates having at least one first limit plate projecting from a longitudinal edge of each said inner middle plate proximate to one end of said longitudinal edge, and at least one second limit plate projecting from said longitudinal edge proximate to the other end of said longitudinal edge, wherein, when said inner middle plates are in said cushioning position, each of said first limit plates of said inner middle plates extends between a respective one of said first regions and a respective one of said second regions of said third and fourth lateral walls of said base plate, and said second limit plates of said inner middle plates extend respectively into said second engaging holes in said base plate.
 9. The packaging box assembly of claim 8, wherein each of said inner middle plates further has a first linking plate that projects from one end of each said inner middle plate proximate to said first limit plate, and a first connecting hole proximate to the first linking plate.
 10. The packaging box assembly of claim 8, wherein said middle plate set further includes two outer middle plates of identical shape, each of said outer middle plates having a plurality of fold lines, a second linking plate projecting from one end of each said outer middle plate and having a second connecting hole, third and fourth linking plates which are formed respectively at the other end of each said outer middle plate and at a middle section of each said outer middle plate and which are turnable and foldable, and at least one third limit plate and at least one fourth limit plate, both of which project from a longitudinal side of each said outer middle plate in a spaced-apart relationship.
 11. The packaging box assembly of claim 8, wherein each of said outer middle plates includes a plurality of split lines, a second linking plate projecting from one end of each said outer middle plate and having a second connecting hole, third and fourth linking plates which are formed respectively at another end and at a middle section of each said outer middle plate through the provision of said split lines and which are turnable and foldable, and third and fourth limit plates both projecting from a longitudinal end of each said outer middle plate in a spaced apart relationship.
 12. The packaging box assembly of claim 11, wherein each of said inner middle plates further has a middle part provided with a linking hole for insertion of said fourth linking plate of a respective one of said outer middle plates.
 13. The packaging box assembly of claim 11, wherein said cover plate further has first and second split lines, a fifth linking plate formed adjacent to a juncture between said central wall and said first lateral wall of said cover plate by using said first split line, and a sixth linking plate formed in said central wall of said cover plate and away from said fifth linking plate by using said second split line.
 14. The packaging box assembly of claim 13, further comprising an auxiliary cover plate connected to one of said lateral walls of said base plate and one of said lateral walls of said cover plate which is at the same side as said one of said lateral walls of said base plate, said auxiliary cover plate having a plurality of elongated slots for insertion of said sixth linking plate.
 15. The packaging box assembly of claim 14, wherein said auxiliary cover plate further has a plurality of fold lines that divide said auxiliary cover plate into a central area, and first, second, third and fourth lateral areas that are formed around said central area, said elongated slots being formed in said central area, said second lateral area having a width larger than that of said first lateral area, said second lateral area being attachable to said one of said lateral walls of said base plate and said one of said lateral walls of said cover plate at said same side, said third and fourth lateral areas being symmetrical to each other and respectively having projecting engaging plates, said engaging plates being respectively insertable into said second engaging holes of said cover plate, said first lateral area being foldable to abut against said cover plate.
 16. The packaging box assembly of claim 13, wherein said base plate further has an ear part projecting from said second region of said first lateral wall of said base plate, and an opening formed in said ear part, said cover plate further has an insert hole formed in said first lateral wall of said cover plate proximate to said central wall of said cover plate, said ear part of said base plate is insertable into said insert hole of said cover plate, and said fifth linking plate of said cover plate is insertable into said opening in said ear part, whereby said cover plate is assembled onto said base plate.
 17. The packaging box assembly of claim 13, wherein each of said first and second lateral walls of said cover plate has two wing plates respectively provided at two opposite ends of each of said first and second regions of said first and second lateral walls of said cover plate, said wing plates of said cover plate respectively having third engaging holes proximate to said first and second regions of said first and second lateral walls of said cover plate, said second regions of said third and fourth lateral walls of said cover plate having lateral connecting plates projecting therefrom proximate to the respective ones of said wing plates of said cover plate, whereby, after said lateral walls of said cover plate are folded, said third engaging holes in two adjacent ones of said wing plates of said cover plate are communicated with each other to permit insertion of a respective one of said lateral connecting plates of said cover plate therein.
 18. A packaging box assembly comprising: a base plate having a central wall, and a plurality of lateral walls extending perpendicularly from said central wall, said central wall and said lateral walls confining a receiving space; a cover plate to close said receiving space, said cover plate having a central wall, and a plurality of lateral walls extending perpendicularly from said central wall of said cover plate, said central wall and said lateral walls of said cover plate confining another receiving space; and a middle plate set including inner middle plates interlockable with said base plate to extend perpendicularly on said central wall of said base plate and to abut against inner surfaces of said lateral walls of said base plate, and outer middle plates interlockable with said cover plate to extend perpendicularly on said central wall of said cover plate and to abut against inner surfaces of said lateral walls of said cover plate, said inner and outer middle plates being higher than said lateral walls of said base plate and said cover plate, respectively, wherein, when said inner and outer middle plates interlock with said base plate and said cover plate, said outer middle plates can be sleeved around said inner middle plates to form a first box configuration, and wherein, when said inner and outer middle plates are separated from said lateral walls of said base plate and said cover plate, said lateral walls of said cover plate can rest on top ends of said lateral walls of said base plate, respectively, to form a second box configuration.
 19. A packaging box assembly comprising: a base plate having a central wall, and a plurality of lateral walls extending substantially perpendicularly from said central wall, said central wall and said lateral walls confining a receiving space above said central wall; and a plurality of inner middle plates disposed perpendicularly on said central wall and abutting against inner surfaces of said lateral walls, said inner middle plates being higher than said lateral walls, at least one of said inner middle plates interlocking releasably with said base plate.
 20. The packaging box assembly of claim 19, wherein said lateral walls include two opposite first and second lateral walls, and two opposite third and fourth lateral walls, each of said lateral walls being divided into a first region proximate to said central wall, a second region distal from said central wall, and a connection region between said first and second regions, said first region being foldable to extend substantially perpendicularly relative to said central wall, said second region being foldable backward over said first region to extend to said central wall, said connection region extending in a plane substantially parallel to said central wall.
 21. The packaging box assembly of claim 20, wherein at least one of said inner middle plates has a first limit plate extending adjacent to said central wall and foldable to extend between and to interlock with said first and second regions of one of said lateral walls.
 22. The packaging box assembly of claim 20, wherein at least one of said inner middle plates has a second limit plate projecting therefrom, said base plate further having at least one engaging hole formed in one of said lateral walls, said second limit plate interlocking with said engaging hole.
 23. The packaging box assembly of claim 20, wherein at least one of said inner middle plates has a second limit plate projecting therefrom proximate to said central wall, said base plate further having an engaging hole formed in said first region of one of said lateral walls and another engaging hole formed in said connection region of said one of said lateral walls, said second limit plate extending outward through said engaging hole in said first region and being inserted into said another engaging hole in said connection region. 